Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 75 , Issue 9
Showing 1-25 articles out of 25 articles from the selected issue
  • Shinsaku Fujita
    Type: scientific monograph
    Subject area: TP
    2002 Volume 75 Issue 9 Pages 1863-1883
    Published: 2002
    Released: September 15, 2002
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    Fundamental concepts proposed for comprehending stereochemical phenomena are described in order to bring out a more systematized format to conventional concepts and terminologies. The concept of coset representation (CR), the symbol of which is G(/Gi), is intuitively introduced by considering the global symmetry G and the local symmetry Gi for an orbit of stereochemically equivalent objects (e.g. atoms in a molecule). The SCR (set-of-coset-representations) notation for classifying molecular symmetries is proposed to remedy the usual insufficient classification based on point groups. According to the chirality/achirality of G and Gi, the sphericity concept (homospheric, enantiospheric, and hemispheric) and the relevant concept of chirality fittingness are proposed to specify the stereochemical phenomena of the G(/Gi)-orbit. The sphericity terms are shown to be superior to the well-known topicity terms (homotopic, enantiotopic, and heterotopic; chirotopic and achirotopic) especially in comprehending complicated stereochemical phenomena. In fact, the topicity terms as well as the terms “stereogenicity and prostereogenicity” and “prochirality” can be derived subsidiarily from the sphericity terms. The concept of subduction of CRs, for which the symbol G(/Gi) ↓ Gi has been coined, is proposed to characterize the desymmetrization of molecules. Thereby, the design of high-symmetry molecules is discussed in term of desymmetrization by atom replacement and by bond replacement. In order to characterize the stereochemistry of non-rigid molecules with rotatable ligands, the concept of proligand/promolecule is proposed; here biphenyl derivatives, methane derivatives, ethane derivatives, and ferrocene derivatives are examined in terms of matched and mismatched molecules. Applications to combinatorial enumeration, symmetry adapted functions, flexible six-membered cyclic compounds, and symmetry numbers are also described.
  • Masahiro Kawasaki, Richard Bersohn
    Type: scientific monograph
    Subject area: TP
    2002 Volume 75 Issue 9 Pages 1885-1900
    Published: 2002
    Released: September 15, 2002
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    Our knowledge of the process of photodissociation is built on a foundation of molecular spectroscopy developed since the 1920’s. However, modern photodissociation dynamics has been mainly created by the introduction of laser light sources around 1970. This review of molecular photodissociation emphasizes findings based on techniques developed in the past ten–fifteen years. These include measurement of the energy dependence of the branching ratios of the yields of different photodissociation channels and the distribution of velocity and internal states of the fragments. The time scale of the separation of the fragments is shown to vary from the microsecond to the femtosecond regime depending on whether the dissociation is indirect or direct. Multiphoton dissociation can be incoherent or coherent. In the latter case, if two different optical paths can accomplish dissociation, changing the relative phase of the transition matrix elements of the two paths can control the branching ratio of different channels. The branching ratio can also be controlled by aligning the parent molecule in an electric field or by using successive ultraviolet and infrared transitions. The review concludes with some applications of photodissociation to the terrestrial atmosphere and to the generation of reactive radical sources.
  • Shigenobu Funahashi, Yasuhiro Inada
    Type: scientific monograph
    Subject area: AI
    2002 Volume 75 Issue 9 Pages 1901-1925
    Published: 2002
    Released: September 15, 2002
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    The solvation structures and the reaction mechanisms of the solvent exchange reactions of metal ions are essential aspects of the interactions of the metal ions with the solvent molecules and information about them is necessary to understand the reactivities of the metal ions in solution. The solvation structures in various coordinating solvents were discussed on the basis of the structure parameters determined by the extended X-ray absorption fine structure technique, referring to the ionic size, ionic charge, and electronic configuration of the metal ions and the bulkiness and electron donating ability of the solvent molecules. It was shown that the deficient bulkiness of 1,1,3,3-tetramethylurea leads to a unique variation in the solvation number for a series of 3d-block metal ions and that the strong electron donating ability of propylamine reduces the solvation number. The solvent exchange mechanisms of various metal ions were discussed on the basis of the activation parameters determined by the nuclear magnetic resonance technique, and the effects of the ionic charge, ionic size, and electronic configuration of the metal ions were regularized. The kinetic results for the solvent exchange of the Ni2+ and Mn2+ ions in a series of nitriles revealed the effect of the solvent bulkiness on the variation in the mechanism. The kinetic chelate effect was pointed out on the basis of the activation parameters for the solvent exchange of the divalent first-row transition metal ions in bidentate solvents such as ethylenediamine and trimethylenediamine.
  • Takeshi Oishi, Koji Ando, Kenjin Inomiya, Hideyuki Sato, Masatoshi Iid ...
    Type: technical report
    Subject area: OB
    2002 Volume 75 Issue 9 Pages 1927-1947
    Published: 2002
    Released: September 15, 2002
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    Total synthesis starting from aldohexoses of naturally occurring α-substituted α-amino acids, (+)-myriocin (1) and (−)-sphingofungin E (2), is described. Overman rearrangement of allylic trichloroacetimidate 6E derived from D-mannose effectively generated the tetrasubstituted carbon with nitrogen, and subsequent Wittig olefination afforded the highly functionalized moiety 3 of myriocin stereoselectively. Sulfone-mediated coupling reaction of the allyl bromide 3 with C12 hydrophobic part 4 successfully constructed the carbon framework possessing E-olefin 28. Removal of the sulfone and protecting groups completed the chiral and stereoselective total synthesis of (+)-myriocin (1). A similar transformation starting from D-glucose also accomplished the total synthesis of (−)-sphingofungin E (2).
  • Shinsaku Fujita
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 9 Pages 1949-1962
    Published: 2002
    Released: September 15, 2002
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    Allene derivatives have been combinatorially enumerated under a point group D2d as well as under a permutation group S9[4], which is a subgroup of the symmetric group of degree 4 and is isomorphic to the point group D2d. These enumerations have been compared in terms of the observance and the vilolation of chirality fittingness, where two types of Young’s tableaus (point-group symmetry and permutation-group symmetry) have been used to clarify the relationship between stereochemistry and permutability of allene derivatives. The concept of chirality/achirality for stereochemistry has been compared with the concept of stereogenicity/astereogenicity for permutability. Enantiomers, which have been characterized by equivalency under point-group symmetry, have been classified into two classes according to whether or not they have been assigned to orbits (equivalence classes) under permutation-group symmetry. On the other hand, diastereomers have been related to equivalence classes (orbits) under permutation-group symmetry only. The terms enantiostereogenic and diastereogenic have been coined to discuss the behavior under permutaiton-group symmetry. The CIP (Cahn–Ingold–Prelog) system is examined in terms of stereogenicity/astereogenicity. A new combination of chirality and stereogenicity described in the present paper provides us with a tool for restructuring stereochemistry.
  • Seiko Nakagawa
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 9 Pages 1963-1966
    Published: 2002
    Released: September 15, 2002
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    The temperature dependence of the formation of negative ions from C6H4XY (X, Y = Cl, Br, I) and cyclo-C6H10X2 (X = Cl, Br) was studied using negative chemical ionization mass spectrometry. The heavier halide ion was mainly observed for C6H4XY. The production rate of halide ions became greater in the order C6H4ClBr << C6H4ClI < C6H4BrI. The relative production rate of the major ions between isomers is related to the character of the substituted halogen atom in the system. The main observed ion was X for C6H10X2. The production rate of halide ions increased in the order cyclo-cis-1,4-C6H10Cl2 < cyclo-trans-1,4-C6H10Cl2cyclo-trans-1,2-C6H10Cl2 << cyclo-trans-1,2-C6H10Br2. For cyclo-trans-1,2-C6H10Br2, not only Br, but also Br2, was observed. Four-center elimination with rotation of the C–Br bond seemed to occur when Br2 was produced from cyclo-trans-1,2-C6H10Br2.
  • Masahiro Manabe, Miharu Kaneko, Takako Miura, Chinami Akiyama, Hideo K ...
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 9 Pages 1967-1972
    Published: 2002
    Released: September 15, 2002
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    The acceleration rate (dα/dXam) of the dissociation degree (α) of ionic SDS micelles to the mole fraction (Xam) of solubilized additives has been determined at infinite dilution by a differential conductivity method. The additives used were a homologous series of amphiphiles with different types of polar groups: alkylglucosides, MEGAs, diols, and cyclooctanol. The method allows us to determine the partition coefficient between the bulk water and the micelles (Kx) and the rate of depression (Csf/Caf) of the monomer surfactant concentration (Csf) to the monomer additive (Caf), in addition to dα/dXam. The results are as follows: (1) dα/dXam in each homologous series is independent of the alkyl chain length, indicating a characteristic value of each polar group. (2) dα/dXam increases with increasing molecular weight of the groups, representing the size effect on the counter ion dissociation. (3) For diols, dα/dXam is higher than twice that of 1-alkanols, due to a large effective size. (4) Kx is dependent on the alkychain length, but independent of the polar group types, indicating that the net charge on the surface of the micelles remains unaltered by solubilization. (5) (Csf/Caf) determined above cmc is identical with the cmc decreasing rate, Δcmc/ΔCa, at cmc.
  • Takao Itoh
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 9 Pages 1973-1976
    Published: 2002
    Released: September 15, 2002
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    The changes of the fluorescence spectral patterns observed when the S2(11Bu) level is approached the S1(21Ag) level by varying the solvent polarizability have been investigated for all-trans-1,6-diphenyl-1,3,5-hexatriene (DPH) and all-trans-1,8-diphenyl-1,3,5,7-octatetraene (DPO) in room temperature solvents. It is shown that the emission of DPO in diiodomethane consists nearly of a 1 : 1 mixture of the S2 and S1 fluorescence and that the emission of DPH in CS2 consists almost entirely of the S2(11Bu) fluorescence. When the 11Bu level approaches the 21Ag level, not only the increase of the S2 fluorescence intensity but also the change in the spectral pattern of the S1 fluorescence are observed for DPH and DPO. The solvent polarizability that achieves the inversion of the 21Ag and 11Bu levels for DPO has been estimated to be 0.54.
  • Kazuhisa Yano, Noritomo Suzuki, Yuusuke Akimoto, Yoshiaki Fukushima
    Type: Others
    Subject area: AI
    2002 Volume 75 Issue 9 Pages 1977-1982
    Published: 2002
    Released: September 15, 2002
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    Mono-dispersed mesoporous silica spheres with ordered hexagonal regularity were synthesized from tetramethoxysilane and dodecyltrimethylammonium bromide as a surfactant under very specific conditions. By adjusting the optimum concentrations of the reactants, silica particles with diverse morphology were obtained at higher initial concentrations. Dilution of the reactants led to the formation of silica spheres with various sizes and relatively less mesoporous regularity. Mono-dispersed silica spheres could not be obtained when hexadecyltrimethylammonium bromide and tetradecyltrimethylammonium bromide were used as surfactants.
  • Ryuichi Arakawa, Kazuyuki Abe, Tsutomu Abura, Yasuo Nakabayashi
    Type: Others
    Subject area: AI
    2002 Volume 75 Issue 9 Pages 1983-1989
    Published: 2002
    Released: September 15, 2002
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    The photolysis of [Ru(bpy)2(bn)]2+ (bpy = 2,2′-bipyridine, bn = 1,4-butanediamine) in acetonitrile and acetone by light of wavelength longer than 420 nm was studied by electrospray ionization mass spectrometry (ESI-MS). The results were different from those of two other amine complexes, [Ru(bpy)2(en)]2+ and [Ru(bpy)2(tn)]2+ (en = ethylenediamine and tn = 1,3-propanediamine). An analysis of the irradiation time course revealed that one end of the bn ligand is quickly dissociated to form a solvent-coordinated complex, [Ru(bpy)2(bn)(AN)]2+ (AN = acetonitrile), and its protonated complex, [Ru(bpy)2(bn + H)(AN)]3+. These solvent-coordinated complexes were not observed in the photochemical reactions of the en or tn complex. The difference in photolysis is due to the fact that the coordination of the bn ligand in [Ru(bpy)2(bn)]2+ is less stable than the en or tn ligand. Both the en and tn complexes formed oxygenated complexes, while the bn complex did not form such a complex. This can be explained by the incorporation of singlet oxygen during the photochemical reaction.
  • Aki Hayashi, Hirokazu Nakayama, Mitsutomo Tsuhako
    Type: Others
    Subject area: AI
    2002 Volume 75 Issue 9 Pages 1991-1996
    Published: 2002
    Released: September 15, 2002
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    In order to develop a new type of adsorbent of toxic heavy metal ions, 2-aminoethanethiol-intercalated layered phosphates were synthesized. 2-Aminoethanethiol was intercalated into titanium(IV) dihydrogenphosphate phosphate dihydrate (γ -titanium phosphate), Ti(H2PO4)(PO4)·2H2O, with a monolayer structure. The intercalation compound could adsorb heavy metal ions, such as Ag+, Hg2+, Cd2+, Pb2+ and Cr3+, by interacting with a mercapto group (–SH). Also, it could completely adsorb Ag+ and Hg2+, even from any concentration of aqueous solutions. The adsorption amounts increased with an increase of the 2-aminoethanethiol content in the intercalation compound. The adsorption mechanism was investigated by using powder X-ray diffraction and solid-state NMR. For a comparison, propylamine-intercalated γ -titanium phosphate was also examined.
  • Takakazu Yamamoto, Mahmut Abla, Yasuharu Murakami
    Type: Others
    Subject area: AI
    2002 Volume 75 Issue 9 Pages 1997-2009
    Published: 2002
    Released: September 15, 2002
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    Reductive elimination of R-R from dialkyl(2,2′-bipyridyl)nickel(II), [NiR2(bpy)] 1 (R = CH3 (1a), C2H5 (1b), n-C3H7 (1c)), caused by π-coordination of electron-accepting aromatic compounds and reductive elimination of Ar-Ar from [NiAr2(bpy)] 2 (Ar = C6F5 (2a) and pyrazolyls (2b and 2c)) promoted by electron-accepting aromatic compounds, Lewis acids, and Brønsted acids have been investigated. 1H-NMR and kinetic data indicate that π-coordination of the electron-accepting aromatic compound to [NiR2(bpy)] leads to the reductive elimination of R-R. The rate of the reductive elimination obeys the second-order rate law, −d[1]/dt = k[1][electron-accepting aromatic compound]. Plots of log k vs Σσp of the electron-accepting aromatic compound give a line with a slope of 1.8. Brønsted acids cause reductive elimination of Ar-Ar from 2 selectively under several reaction conditions (e.g., 2a with CF3COOH in air and 2b with HBr). The reductive elimination reaction of 2a caused by CF3COOH obeys the second-order rate law, −d[2a]/dt = k′[2a][CF3COOH], in air. The reaction of 2b with H2SO4 requires O2, giving the rate equation, −d[2b]/dt = k′′[2b]2[O2]; k′′ increases with [H2SO4], reaching a maximum value at a high [H2SO4]. UV-vis spectroscopy reveals the presence of the following equilibrium: 2b + H2SO4 2b·H2SO4, and the equilibrium constant Ka is evaluated as Ka = [2b·H2SO4]/([2b][H2SO4]) = 47 M−1 at 300.5 K. UV-vis data give information about the electronic states of 2 and the 2b-Brønsted acid adduct. Poly(6-hexylpyridine-2,5-diyl) with a higher molecular weight has been prepared according to the basic information.
  • Jong-Wan Lim, Yu-Chul Park, Masahiro Mikuriya
    Type: Introduction
    Subject area: AI
    2002 Volume 75 Issue 9 Pages 2011-2012
    Published: 2002
    Released: September 15, 2002
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    A cis-dioxomolybdenum(VI) complex with N′, N′-bis(2-hydroxy-3,5-dimethylbenzyl)-N, N-dimethylethylenediamine (H2L), cis-[MoO2(L)], was synthesized and characterized by measurements of NMR, infrared, and electronic spectra. The X-ray crystal structure shows that the compound has a distorted octahedral geometry with an N2O4 coordination environment.
  • Yasuo Saitoh, Makoto Kaneko, Katsunori Segawa, Hiroki Itoh, Hirochika ...
    Type: Others
    Subject area: OB
    2002 Volume 75 Issue 9 Pages 2013-2023
    Published: 2002
    Released: September 15, 2002
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    Photocleavage of the N–O bond of N-(9-anthroyloxy)-9-fluorenylideneamine and its 1-and 2-anthroyloxy derivatives takes place efficiently in acetonitrile in the excited singlet state attributed to the fluorenylidene moiety. This made it possible for the first time to directly observe anthroyloxyl radicals by the transient absorption method. The quantum efficiency for photocleavage decreases remarkably in benzene, in which the lowest excited singlet state is attributed to the anthroate moiety. All the three kinds of anthroyloxyl radicals are much less reactive in decarboxylation, addition to olefins, and hydrogen-atom abstraction than benzoyloxyl and 1- and 2-naphthoyloxyl radicals; 9-anthroyloxyl radicals supposedly undergo intramolecular addition–elimination in the ipso-position in equilibrium with α-lactonic spirodihydroanthryl radicals, as indicated by one-color and two-color laser photolyses.
  • Yoshio Furusho, Yow-hei Sohgawa, Nobuhiro Kihara, Toshikazu Takata
    Type: Others
    Subject area: OB
    2002 Volume 75 Issue 9 Pages 2025-2029
    Published: 2002
    Released: September 15, 2002
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    Ethyl cinnamate was allowed to react with nitrogen monoxide (NO) by photoirradiation in the presence of metallosalen complexes (4), oxygen, and axial ligands for 4 to yield furoxan derivatives (6). Oxygen and axial ligands are indispensable for this reaction. Photoirradiation enhanced the yield of 6. Lowering the reaction temperature increased the yield of 6 up to 55% (at −5 °C).
  • Tetsuya Nakamura, Samar Kumar Guha, Yoshihiro Ohta, Daisuke Abe, Yutak ...
    Type: Others
    Subject area: OB
    2002 Volume 75 Issue 9 Pages 2031-2041
    Published: 2002
    Released: September 15, 2002
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    Toward the elucidation of the origin of the “syn-effect,” the stereochemistry of the isomerization of (E)-α-fluorovinylic sulfones to the corresponding allylic sulfones under mild basic conditions was investigated. The ratio of (Z)-isomers of the resulting allylic sulfones decreased in the following order for the γ-substituents of the starting vinylic sulfones: F- > EtO- > CH3- > BnS- > CH3CH2- > (CH3)2CH- > (CH3)3C-, C6H5-. The fluorine atom showed the highest “syn-effect,” which is herein defined as an effect that stabilizes the syn-conformation in the transition state against a steric or nonbonded repulsion; the rest of the series was in accord with previous results found in the conversion of α-unsubstituted (E)-vinylic sulfones to the corresponding allylic sulfones under similar conditions. These results were rationalized based on the σ→π* interaction.
  • Yoshimi Sueishi, Chiharu Yoshioka, Claudio Olea-Azar, Lester A. Reinke ...
    Type: Others
    Subject area: OB
    2002 Volume 75 Issue 9 Pages 2043-2047
    Published: 2002
    Released: September 15, 2002
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    Hydroxyl and phenyl radical spin trapping rates by α-phenyl-N-t-butylnitrone (PBN, N-benzylidene-t-butylamine N-oxide) and its analogs were determined using a competitive trapping method. Hydroxyl radical was generated from hydrogen peroxide in water using UV photolysis, in the presence of the selected spin trap plus 5,5-dimethyl-pyrroline N-oxide (DMPO). Phenyl radical was produced with UV photolysis of tetraphenyllead, and spin trapping was performed in benzene. Spin trapping rate constants were calculated using EPR signal intensity ratios for the DMPO spin adducts vs PBN-type spin adducts. The rate constants were strongly dependent on the kind of substituent in the spin trap; the magnitude of the substituent effect was also dependent on the kind of free radicals trapped, i.e., hydroxyl or phenyl radicals. For example, in phenyl radical trapping, the spin trapping rate in hydroxy-substituted PBNs followed Hammett’s equation, while there is no such correlation in hydroxyl radical trapping. Hydroxy-substituted PBNs such as 2-, 3-, and 4-hydroxy-PBNs showed much lower apparent spin trapping rates than that of PBN. The reaction between hydroxyl radical and phenoxyl group is a likely cause.
  • Shin-ichi Usugi, Hideki Yorimitsu, Hiroshi Shinokubo, Koichiro Oshima
    Type: Others
    Subject area: OB
    2002 Volume 75 Issue 9 Pages 2049-2052
    Published: 2002
    Released: September 15, 2002
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    Treatment of silyl enolates with methyllithium followed by an addition of gallium trichloride afforded the corresponding gallium enolates. The reaction of the resulting gallium enolates with α-halo carbonyl compounds in the presence of triethylborane as a radical initiator provided 1,4-dicarbonyl compounds in good yields.
  • Kensuke Naka, Takashi Uemura, Yoshiki Chujo
    Type: Others
    Subject area: OB
    2002 Volume 75 Issue 9 Pages 2053-2057
    Published: 2002
    Released: September 15, 2002
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    The mixing of 2-benzylidene-4-phenyl-1,3-dithiole and cyclobis[4,4′-bipyridinium-1,1′-diyl-1,4-phenylenebis-(methylene)] as a cyclic acceptor in DMSO produced a green-brown solution, which showed a charge-transfer (CT) absorption band with a peak at 616 nm. The 1H NMR spectrum of the dithiole, after adding the cyclic acceptor in DMSO-d6, showed upfield shifts of the peaks for the dithiafulvene moiety. These facts indicated that an insertion of the dithiole into the cyclic acceptor by a CT interaction led to the formation of a pseudorotaxane. The self-assembly of π-conjugated dithiafulvene polymers and the cyclic acceptor by a CT interaction gave pseudopolyrotaxanes in DMSO. The UV-vis and 1H NMR spectra of the pseudopolyrotaxanes suggest that the incorporation ratio of the cyclic acceptors into the polymers depends on the molecular weights of the polymers. The polymers with lower molecular weights seem to be more favorable for polyrotaxane formation. After self-complexation of the polymer with the cyclic acceptor, an anodic shift of the oxidation potential of the dithiafulvene unit was observed in the cyclic voltammogram. In addition, the effective CT interaction between the dithiafulvene unit and the cyclic acceptor afforded a high conductivity of the pseudopolyrotaxane.
  • Mitsuhiro Okimoto, Yukio Takahashi
    Type: Introduction
    Subject area: OB
    2002 Volume 75 Issue 9 Pages 2059-2060
    Published: 2002
    Released: September 15, 2002
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    Benzil hydrazones were subjected to electrolytic oxidation in MeOH containing a halide ion source, such as KI and KBr. The results show that the reaction products were dependent on both the electrolytes and the substituents. In the presence of KI, benzoylphenyldiazomethanes were obtained, whereas in the presence of KBr, benzil dimethyl acetals were obtained.
  • Isao Shiihara
    Type: Others
    Subject area: AM
    2002 Volume 75 Issue 9 Pages 2061-2066
    Published: 2002
    Released: September 15, 2002
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    In a previous report (Ref. 1), the author described the chemical structure of acetone powder (AP, the so-called laccase) of the Japan urushi sap, and dope obtained by the classic Kurome process is interpreted as urushiol orthosilicate. In this paper, the further discussion is given about flake pieces which were accidentally obtained from a broken Al tube containing raw urushi during the summer; also described is dope obtained under a special treatment (three ceramic rolls mill (TR) compounding) and hardening while keeping at room temperature and 80% humidity. Precise studies have shown that both have hexagonally and octahedrally oriented oxygen atoms around the center Si atom of the acetone powder. It has been found that three kinds of urushiol silicate and inorganic bond (peroxide) bridging formation, such as –H2C–O–OCaOH or –H2C–O–OMgOH, are the true hardening mechanisms, instead of a hitherto considered enzyme action.
  • Hyeyoung Park, Eung-Ryul Kim, Dong Jin Kim, Haiwon Lee
    Type: Others
    Subject area: AM
    2002 Volume 75 Issue 9 Pages 2067-2070
    Published: 2002
    Released: September 15, 2002
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    Four kinds of azo dyes and their metal-azo dyes were synthesized in order to obtain a high reflective index and better thermal stability as a recording material for DVD-R. Several kinds of novel azo dyes based on benzoic acid, 6-methoxybenzothiazole, benzothiazole-6-carboxylic acid, and benzimidazole have been synthesized. These azo dyes reacted with metal ions, such as Ni2+, Cu2+, Zn2+, and Co2+, as ligands. All structures of the compounds were confirmed by 1H-NMR and FT-IR analyses. The optical and thermal properties of azo dyes and their metal-azo dyes were characterized by UV-vis and TGA analyses. In the UV-vis spectra, the absorption maxima of metal-azo dyes show at longer wavelength than those of azo dyes. These spectral shifts are affected by substituent groups, electron-donating or -withdrawing groups, of azo dyes and metal ions. The metal-azo dyes were thermally stable up to 300 °C, which were confirmed by TGA analyses. Particularly, in the case of an azo dye complexed with Zn based on 6-methoxybenzothiazole, good absorption at 635 nm was observed, and its thermal stability was maintained up to 300 °C, with high refractive index of about 2.08.
  • Setsuko Irie, Masahiro Irie
    Type: Others
    Subject area: AM
    2002 Volume 75 Issue 9 Pages 2071-2074
    Published: 2002
    Released: September 15, 2002
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    The effect of the addition of metal complexes and aromatic compounds on the radiation-induced coloration of polystyrene films containing 1,2-bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclopentene was examined to develop a sensitive reusable color plastic dosimeter. By the addition of metal complexes, the radiation sensitivity increased along with an increase in the atomic numbers. When aromatic compounds, such as naphthalene, biphenyl, and acenaphthene, were added to the polymer film, the coloration sensitivity increased, while the addition of anthracene and pyrene decreased the sensitivity. Excitation energy transfer from the sensitizers to the dithienylethene is considered to play an important role in the radiation-induced coloration in polystyrene films containing the additives.
  • Keisuke Hirano, Seiji Yamaoka, Satoshi Minakata, Mitsuo Komatsu
    Type: Others
    Subject area: AM
    2002 Volume 75 Issue 9 Pages 2075-2078
    Published: 2002
    Released: September 15, 2002
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    Dimethyl 1,2-dihydropyrrolo[1,2-a]quinoxaline-2,3-dicarboxylate is red colored in the solid state, while it is a small molecule and has no hydrogen-bonding interaction. This unusual color property was investigated by means of electronic characterization in solution and in the solid state. The push-pull system from electron-donating pyrrole nitrogen to the electron-withdrawing 3-methoxycarbonyl moiety causes a spectral shift to an orange color in the visible region. An X-ray structure analysis indicated that these polar molecules (μ = 7.6 D) are arranged in a zig-zag fashion so as to minimize the electrostatic energy. As a consequence, the absorption band is presumably shifted toward longer wavelengths by about 60 nm (about 2508 cm−1) in going from a solution to the solid state. These results lead to a large bathochromic shift in the absorption spectrum, resulting in the red color of this compound in the solid state.
  • Ryoka Matsushima, Katsuaki Kato, Shinichi Ishigai
    Type: Introduction
    Subject area: AM
    2002 Volume 75 Issue 9 Pages 2079-2080
    Published: 2002
    Released: September 15, 2002
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    Photochromic reactions of some substituted 2-hydroxychalcones [3-(2-hydroxyphenyl)-1-phenyl-2-propen-1-ones] have been studied in solid hydrogel matrices. The results demonstrated good reversibilities for the chalcone-flavylium interconversion. Thus, in an agar-gel matrix the coloration-decoloration could be repeated over 50 cycles without significant fatigue. In a silica sol-gel matrix, a fairly good reversibility was obtained up to ca. 30 cycles; in the later cycles, however, extensive degradations took place.
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